An image forming apparatus of the related art, such as a copier, a printer, a facsimile apparatus, or a multifunction apparatus equipped with these multiple functions, contains a cleaning device including a cleaning member that rotates so as to remove residual toner from an intermediate transfer belt looped between multiple rollers and a toner recovery roller that electrically recovers the toner from the cleaning member.
The cleaning device is configured to wipe off and remove, at a downstream side relative to a secondary transfer unit as viewed in a rotating direction of the intermediate transfer belt, residual toner remaining on the surface of the intermediate transfer belt after a toner image primarily transferred on the intermediate transfer belt from an electrophotographic photosensitive body is secondarily transferred onto transfer paper. The residual toner remaining on the surface of the intermediate transfer belt is collected between brush fibers of the cleaning member made of a roller-shaped fur brush by rotating the cleaning member in a counter direction of the rotating direction of the intermediate transfer belt. Subsequently, the residual toner collected between the brush fibers is electrostatically recovered by applying a bias to the toner recovery roller that is in contact with the cleaning member in an engaged manner. In detail, the tension of the intermediate transfer belt looped between at least two rollers (e.g., a driving roller and a driven roller) is maintained by using the driven roller or another roller as a tension roller, and the fur brush serving as the cleaning member is disposed so as to face this tension roller across the intermediate transfer belt.
In this case, the tension roller and the fur brush form a cleaning area by bringing the outer periphery of a first holding member rotatably holding the fur brush and the outer periphery of a second holding member rotatably holding the tension roller into contact with each other.
Regarding the toner recovery roller that electrically recovers the toner from the fur brush, a bearing portion of the toner recovery roller and a bearing portion of the fur brush are integrally formed with a single component, and the fur brush is made rotatable about the bearing portion of the toner recovery roller.
If the tension roller is made rotationally displaceable so as to apply tension to the intermediate transfer belt, the tension applied by the tension roller to the intermediate transfer belt may be set greater than the pressure applied by the fur brush to the intermediate transfer belt so that if the tension roller is installed in a plurality, the fur brush can be attached to any one of the tension rollers.
In the aforementioned cleaning device, the bearing portion of the fur brush and the bearing portion of the toner recovery roller are integrally formed with a single component and the fur brush is made rotatable about the bearing portion of the toner recovery roller, and the cleaning area is formed by bringing the outer periphery of the first holding member rotatably holding the fur brush and the outer periphery of the second holding member rotatably holding the tension roller into contact with each other. In this case, if the amount of displacement of the tension roller becomes large due to, for example, a variation in the inner perimeter of the intermediate transfer belt or a variation in the bias load of the tension roller, a rotational displacement amount of the fur brush that is rotationally displaceable around the bearing portion of the toner recovery roller would also become large. Therefore, if a cleaning case that supports the fur brush, the toner recovery roller, and the like is fixed within a main body of the image forming apparatus, the fur brush may possibly rotationally move in a direction that causes a gap between the cleaning case and the brush surface of the fur brush to increase.
When the gap between the cleaning case and the brush surface of the fur brush increases, toner accumulating inside the cleaning case with the rotation of the fur brush may unfavorably splatter outward of the cleaning case or spill from an opening of the cleaning case.
Conceivable techniques for enhancing cleaning performance using a fur brush include, for example, optimizing brush conditions, such as brush elasticity, brush fineness (thickness), brush density, and brush resistance value, or changing conditions by increasing a bias potential applied to the toner recovery roller so as to increase a bias potential difference between the fur brush and the toner recovery roller. However, when the gap between the cleaning case and the brush surface of the fur brush increases, simply changing these various conditions is not sufficient because clogging may tend to occur readily in the brush, depending on a set amount by which the toner recovery roller engages into the fur brush, and the fur brush may contract and decrease in outer diameter. This can lead to a problem of deteriorated cleanability at cleaning sections (i.e., a contact section between the fur brush and the intermediate transfer belt and an engagement section between the fur brush and the cleaning member).
Furthermore, although increasing the amount by which the toner recovery roller engages into the fur brush enhances recovery performance of the toner recovery roller in addition to enhancing cleanability and exhibiting a toner-spillage reduction effect, an increase in torque in the fur brush may occur readily.
When an idling period (stopped period) in which an image forming process is not performed is long, the brush fibers of the fur brush may become deformed and stay in a flattened state, resulting in problems such as defective cleaning and speed variation caused by torque fluctuation.
In addition, when the amount of displacement of the tension roller becomes large as mentioned above, if a blade member, which is for scraping off the toner and is in contact with the fur brush at an upstream side, in the rotating direction, relative to an engagement position of the toner recovery roller, is provided, the amount of engagement between the blade member and the fur brush would deviate from a predetermined amount, resulting in a difficulty in maintaining stable cleaning performance.